Chronic Drought Stress of Common Lawn Turf Species in the United States Transition Zone.

Urban water supply is critically important in a rapidly growing United States population; this research highlights the importance of water use efficiency in urban turf landscapes. A greenhouse chronic drought stress trial was conducted in Lubbock, TX. Three common turfgrasses species grown in the transition zone were chosen: tall fescue (Festuca arudinacea Schreb.), buffalograss (Buchloe dactyloides Nutt, Engel.), and bermudagrass (Cyonodon dactylon Pers.). Supplemental irrigation was applied at 89, 74, 59, or 44 ml per application three times per week, which is equivalent to 3.2, 2.6, 2.1, or 1.6 cm per week, respectively. Variations in volumetric water content were confirmed with TDR measurements. Visual turf quality and leaf firing were obtained two times per week along with digital image analysis and NDVI to assess drought responses of species. Canopy temperature and photosynthetic measurements provided a physiological response of drought to these turf species. Lastly, root length and dry mass were ascertained at the conclusion of each experiment. No statistical differences in rooting parameters were observed; therefore, differences among turf species are indicative of drought tolerance responses. Buffalograss net photosynthesis provided positive slope for all irrigation levels, which corresponds with minimal leaf firing observed. Bermudagrass had highest mean percent green cover and NDVI when combining all irrigation levels. Heat within the greenhouse negatively impacted net photosynthesis of tall fescue overall; however, percent green cover, and canopy temperature were similar to other turf species for 11 days of variable irrigation before drought symptoms became evident. Applying 74 or 89 ml of water three times per week provided statistically similar results for all parameters compared to lower irrigation levels. This research demonstrates the drought tolerance capabilities of turf species commonly used in residential landscapes within the transition zone and the physiological response of the species to chronic drought stress.